Single Point Comparison
1. Purpose
This procedure outlines the single-point comparison method for calibrating temperature sensors used in cold rooms, refrigerators, and freezers. The method compares the reading from a master thermometer against the target sensor to determine calibration accuracy.
2. Scope
This procedure applies to all temperature sensors monitored in the Didge platform that require periodic calibration, in facilities such as catering kitchens, cold storage, hospitals, aviation catering units, and other temperature-controlled environments.
3. Equipment & Materials
Master Thermometer – Pre-calibrated or new infrared thermometer of good quality (accepted as accurate if new or with valid calibration certificate).
iPad / Mobile Device – With access to the Didge Calibration Module.
Access to Target Sensor Locations – Cold rooms, fridges, or freezers.
4. Definitions
Master Temperature: Temperature reading from the master thermometer.
Target Unit: Sensor under calibration.
Variance: Difference between Master Temperature and Target Unit temperature.
Pass Criteria: Variance within ±1.0°C of Master.
5. Responsibilities
Technician / Operator: Perform calibration following this procedure.
Supervisor: Verify calibration results and ensure corrective actions are completed if required.
6. Procedure
6.1 Preparation
Verify the master thermometer is functioning correctly and clean.
Ensure mobile device is connected to the Didge Calibration Module.
Select Single-Point Calibration Operation from the calibration menu.
6.2 Performing the Calibration
Select Sensor:
From the calibration screen, choose the target sensor/unit.
The Didge system will display the latest live temperature reading from that sensor.
Measure Master Temperature:
Go to the physical location of the sensor (inside cold room, fridge, or freezer).
Position the master thermometer as close as possible to the sensor location.
Allow the reading to stabilise, then record the temperature.
Input Master Temperature:
Enter the reading from the master thermometer into the Master Temperature field in Didge.
System Calculation:
The Didge platform will automatically calculate the variance between the master and target unit.
Evaluate Calibration Status:
If the variance is ≤ ±1.0°C, status = Pass.
If the variance is > ±1.0°C, status = Fail.
Apply Corrective Actions (if Fail):
Replace sensor.
Contact vendor for service.
Replace batteries.
Other corrective action (specify).
Submit Record:
Select Complete when calibration is finished.
Tap Submit to save calibration record for the unit.
6.3 Repeat for All Units
Perform this process for each unit/sensor scheduled for calibration.
Operators typically move through the facility carrying an iPad and performing calibrations in real time.
7. Records & Documentation
Calibration records are automatically stored in the Didge platform.
Retain calibration certificates for master thermometers as per QA policy.
8. References
Didge Calibration Module User Manual.
Manufacturer guidelines for infrared thermometers.
ISO 9001:2015 – Clause 7.1.5.2 (Measurement traceability).
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